Recently, digital systems are being complicated day by day, and the number of High-Definition Multimedia Interface (HDMI) terminals among various external inputs of the digital systems is on the increase.
The HDMI provides an integrated channel of pre-existing RGB, Y, and Cb/Cr channels and audio channels. The HDMI is a technology that combines High-Definition (HD) video signals and multichannel audio signals into a single digital interface with a bandwidth of 5 Gbps or more.
Also, the HDMI includes three independent communication channels of a Transition Minimized Differential Signaling (TMDS) channel, a Display Data Channel (DDC), and a Consumer Electronics Control (CEC) channel, which can be used to transmit/receive A/V data, device information, and control commands.
The CEC is an additional protocol for performing a high-level control function in the HDMI, which can be used in the environments of a low transmission rate and a small-capacity memory.
In conclusion, recent display devices have a HDMI-CEC function for users' convenience and thus can control various external devices such as DVDs and STBs. Accordingly, the users can enjoy desired video contents by connecting various external devices to the external input terminals of the display devices.
However, if no user restriction is set, the external devices connected through the external input terminals can be used by adolescent boys or children without restriction. What is therefore required is a use restriction function that can selectively restrict the indiscreet use of the external devices by adolescent boys or children.